Surface properties-dependent antifungal activity of silver nanoparticles

Abstract

Silver nanoparticles (AgNPs) exhibit unusual biocidal properties thanks to which they find a wide range of applications in diverse fields of science and industry. Numerous research studies have been devoted to the bactericidal properties of AgNPs while less attention has been focused on their fungicidal activity. Our studies were therefore oriented toward determining the impact of AgNPs characterized by different physicochemical properties on Fusarium avenaceum and Fusarium equiseti. The main hypothesis assumed that the fungicidal properties of AgNPs characterized by comparable morphology can be shaped by stabilizing agent molecules adsorbed on nanoparticle surfaces. Two types of AgNPs were prepared by the reduction of silver ions with sodium borohydride (SB) in the presence of trisodium citrate (TC) or cysteamine hydrochloride (CH). Both types of AgNPs exhibited a quasi-spherical shape. Citrate-stabilized AgNPs (TCSB-AgNPs) of an average size of 15 ± 4 nm were negatively charged. Smaller (12 ± 4 nm), cysteamine-capped AgNPs (CHSB-AgNPs) were characterized by a positive surface charge and higher silver ion release profile. The phytopathogens were exposed to the AgNPs in three doses equal to 2.5, 5 and 10 mg L−1 over 24 and 240 h. Additionally, the impact of silver ions delivered in the form of silver nitrate and the stabilizing agents of AgNPs on the fungi was also investigated. The response of phytopathogens to these treatments was evaluated by determining mycelial growth, sporulation and changes in the cell morphology. The results of our studies showed that CHSB-AgNPs, especially at a concentration of 10 mg L−1, strongly limited the vegetative mycelium growth of both species for short and long treatment times. The cell imaging revealed that CHSB-AgNPs damaged the conidia membranes and penetrated into the cells, while TCSB-AgNPs were deposited on their surface. The fungistatic (lethal) effect was demonstrated only for silver ions at the highest concentration for the F. equiseti species in the 240 h treatment. The number of spores of both Fusarium species was significantly reduced independently of the type of silver compounds used. Generally, it was found that the positively charged CHSB-AgNPs were more fungicidal than negatively charged TCSB-AgNPs. Thereby, it was established that the stabilizing agents of AgNPs and surface charge play a crucial role in the shaping of their fungicidal properties.

Antifungal Properties of Nanosilver Clay Composites Against Fungal Pathogens of Agaricus bisporus

“…were obtained in this study, greater antifungal activity was anticipated. Zeolite and montmorillonite had uniformly distributed, smaller AgNPs, which may be attributed to their flatter matrix structures that provided a greater surface area for AgNP adhesion [39,40] . Compared to zeolite and montmorillonite, palygorskite had fibrous rod structures, resulting in a lower surface area to bind individual AgNPs.…”

“…Zeolite and montmorillonite had uniformly distributed, smaller AgNPs, which may be attributed to their flatter matrix structures that provided a greater surface area for AgNP adhesion. [39,40] Compared to zeolite and montmorillonite, palygorskite had fibrous rod structures, resulting in a lower surface area to bind individual AgNPs. Due to this, NPs produced from palygorskite usually occur as aggregates and clusters of large-sized NPs.…”

Topologically Zn2+ hybridized ZnS nanospheres (Zn2+/nZnS) efficiently restrained the infection of Fusarium verticillioides in rice seeds by hyphal disorganization and nutritional modulation

“…72,73 Surface modifications affect the bio-uptake and translocation of nanoparticles and studies indicate the favorable effect of imparting a positive surface potential on nano surfaces owing to the higher cellular uptake efficiency than neutral and negatively charged nanoforms. 23,24 Various analogous studies reported the size-dependent augmented uptake of positively charged inorganic metal nanoparticles with better effects. [25][26][27] Thus, the present experimental results indicate that the positive topology of ZnS nanoforms show a superior outcome as a nano fungicide and nutritional fertilizer.…”

“…23 Positively charged nanoparticles are reported to augment the electrostatic interaction between the fungal wall glycoprotein (negatively charged), leading to morphological changes, shrinkage of the cytoplasm, disruption of DNA and RNA synthesis, and ultimately hyphal death. 24,25 Besides their in vitro potential, positive nanoforms are proven to exhibit good accumulation, distribution and assimilation in biosystems, enhancing their applications. 26,27 There are many knowledge gaps that need to be filled by agrochemists in terms of the effect of an enhancement in surface charge on pathological and phyto-quality parameters.…”

Silversol®(a colloidal nanosilver formulation) inhibits growth of antibiotic-resistantStaphylococcus aureusby disrupting its physiology in multiple ways

“…Modern times has also witnessed numerous reports (Burange et al, 2021; Korkmaz, 2020; Khan et al, 2023) describing different types of biological activities of silver. Antimicrobial activity of different forms of silver has also been documented e.g., antiviral (Balasubramaniam et al, 2020; Jain et al, 2021; Ratan et al, 2021), antibacterial (Balasubramaniam et al, 2020; Ibrahim et al, 2020; Bruna et al, 2021), antifungal (Mussin et al, 2022; Matras et al, 2022), antiprotozoal (Abou Elez et al, 2023), and anthelmintic (Majumdar and Kar, 2023; Gajera et al, 2023a). Different forms of silver (e.g., metallic, colloidal, silver salts) may have different mechanisms of action, and varying magnitude of biological activity.…”